Standalone water purification systems, which have been commercially available for decades, are used principally in laboratory environments to provide highly purified and high quality reagent grade water for various applications, including chemical analysis and physical testing. Ordinary tap water contains a variety of contaminants or impurities, including dissolved organics, dissolved inorganics, dissolved gases, suspended particles, microorganisms, and byproducts from bacterial degradation. Water purification systems remove a substantial portion of these contaminants and impurities to generate reagent grade water.
Various standards are employed to specify the purity of reagent grade water. One such standard setting forth requirements for water suitable for use in methods of chemical analysis and physical testing is the commonly-accepted standard D1193-99e1 “Standard Specification for Reagent Water” established by the organization ASTM International (West Conshohocken, Pa.). Under this standard, the highest quality reagent grade water, which conforms to, or exceeds, ASTM Type I standards, is generally used in applications like high performance liquid chromatography (HPLC), atomic absorption (AA) spectrometry, and tissue culture. The ASTM Type II grade of reagent water, which has a lower purity than ASTM Type I reagent grade water, may be used for hematological, serological, and microbiological procedures. Reagent grade water suitable for general laboratory qualitative analyses, such as urinalysis, parasitology, and histological procedures, conforms to ASTM Type III standards. The ASTM Type IV grade of reagent water, which conforms to the least stringent standards, is used in applications where these relaxed purity requirements are permitted.
Conventional water purification systems may include a main purification unit that contains a pump that forces water through a fluid circuit and a water purification device capable of removing unwanted contaminants and impurities from water circulating in the fluid circuit. The water purification device may rely on a number of familiar purification techniques, including filtration, single or multiple distillation, sorption, and ion exchange, for removing impurities from the circulating water. The main purification unit often includes a manually operated tap or dispensing valve positioned at a convenient location on the main purification unit that diverts reagent grade water from the fluid circuit for fixed dispensing.
Certain applications dictate the need for a capability of dispensing reagent grade water at a location remote or removed from the main purification unit. A detached dispensing apparatus, which may have the form of a gun or another form such as a solenoid, may be fluidly connected to the main purification unit by a length of flexible tubing. The tubing conveys a flow of reagent grade water from the main purification unit to the remote dispensing apparatus. The dispensing apparatus may be positioned relative to the main purification unit within the spatial limits imposed by the length of the flexible tubing for remotely dispensing reagent grade water. A stream of reagent grade water is continuously circulated through the tubing coupling the main purification unit with the dispensing apparatus and through the dispensing apparatus. When the dispensing apparatus is manually actuated, reagent grade water is dispensed.
Use of a remote dispensing apparatus in a water purification system also conserves space on the bench-top because the main purification unit can be positioned, for example, either under the bench, at the back of the bench, or high on a wall. In certain designs, the remote dispensing apparatus is removably supported in a bracket integrated into the main purification unit and may be optionally used for fixed dispensing local to the main purification unit when mounted in the bracket. Other ways of supporting a remote dispensing apparatus include a wall-mounting bracket or a bracket on a bench-top stand. When removed from the bracket and hand held to dispense purified reagent grade water into a container, the remote dispensing apparatus must be gripped at all times while depressing a gun trigger or with the gun trigger locked.
The remote dispensing apparatus may include electrical components that communicate with the main purification unit across a hard-wired communications link. For example, a remote dispensing apparatus may feature a flow control solenoid that is opened and closed by an electrical signal communicated through conductors inside a cable extending from the main purification unit. However, such cables tend to become entangled with nearby obstacles. Cables also have a finite length and are terminated by electrical connectors on each end. Hence, cable length may be adjusted only by installing a different cable. If a cable is too short, a longer cable must be installed. If the remote dispensing apparatus is moved closer to the main purification unit than the cable length, the unused length of the cable may prove cumbersome and unwieldy. Lengthy leads may also be susceptible to electrical noise or cause electrical noise that interferes with the operation of adjacent noise-sensitive devices. Another deficiency of conventional main purification units is that most only include a single connection point for the cable, which limits the main purification unit for use with only a single remote dispensing apparatus.
Multiple remote dispensing apparatus may be coupled with a single main purification unit by running lengths of tubing of a water loop and electrical cables from the unit to each of the remote dispensing apparatus. In some facilities, an existing fluid loop may extend through the room walls to connect different rooms in which one or more of the remote dispensing apparatus are situated. However, a facility that lacks an existing fluid loop will require remodeling or refurbishing to alter the structure to add a fluid loop servicing multiple rooms. The cabling of remote dispensing apparatus in different facility rooms also presents difficulties. Each of the remote dispensing apparatus should include a cable extending in association with the fluid loop to the main purification unit. The wire gauge scales upwardly with increasing cable length, which increases the cumbersomeness and unwieldiness of the cables. Fluid loops in newly constructed facilities must include associated cabling for establishing communication between the remote dispensing devices and the main purification unit.
In view of these and other deficiencies of conventional water purification systems, it would be desirable to dispense reagent grade water with one or more remote dispensing devices that lack a hard-wired connection with the main purification unit.